1. Field of the Invention
The invention relates generally to devices for shredding pruned plant material into particle size. More specifically, the invention pertains to a self propelled field shredder, adapted to pass through an orchard, pick up pruned branches from the ground, and shred the branches into sawdust and small shredded particles. The consistency and size of the shredded material is such that it rapidly decomposes in the field and enriches the soil in the orchard.
2. Description of the Prior Art
Orchard trees, such as almonds, pistachios, and walnuts, are typically pruned at the end of each harvest season. This pruning is undertaken to shape and size the trees, as well as to improve their production. The pruned material may range in size from small twigs to branches up to four inches in diameter. As pruning crews move through the orchard, the cut twigs and branches are simply dropped into piles between rows of the trees. Later, individual piles are pushed by machinery and consolidated into larger piles at the end of the rows. Then, the large piles are burned under controlled conditions, to eliminate all trace of the cuttings.
This process is labor consuming, because the material has to be moved considerable distances from where it was cut. In addition, agricultural burning of cuttings and like material, has fallen into disfavor, owing to the air pollution it necessarily produces. It appears likely that new Federal and State air pollution standards will severely limit or even eliminate large scale agricultural burning of this sort, in the near future.
In lieu of burning branch cuttings, chipping or shredding machines have been used in some applications either to cut up or to pulverize pruned material into relatively small pieces.
A conventional chipper uses knives mounted on a rotating flywheel or a drum. The material is held fast by a stationary shear bar or anvil as the knives pass close by. Chippers may also use infeed rollers to pull material into the machine and force it against the knives and anvil. The small chips produced by the cutting action of the knife and anvil arrangement are discharged through a chute.
When chippers are used to process tree cuttings, they are mounted on a truck body or on a trailer frame so they can be moved into a position close to the pruning operation. These mobile chippers are used primarily by utility crews for power or telephone service. Workers manually feed the chipper by pushing the branches into a rear positioned hopper. A rotating element, such as a drum or a disc having sharp blades on a cutting surface, aggressively draws branches into the chipper. The processed material may be stored in a bin mounted on the truck, or it may be discharged into a pile on the ground.
Shredders, by way of contrast, usually employ a rotatable element in conjunction with a screen. The rotatable element hammers, flails, or grinds the material into small pieces. When the pieces are small enough, they pass through perforations in the screen and are discharged. The most common shredder design uses a series of metal strips mounted on a rotating shaft. This type of shredder, known as a xe2x80x9cHammer Millxe2x80x9d, forces the incoming material against a curved, perforated plate until it is broken up and shredded sufficiently to pass through the perforations.
The chipped, slivered, or shredded material may be used for ground cover or compost. However, the size and consistency of the material discharged by conventional chippers and shredders is such that it will not decompose quickly, and it cannot be added directly to soil to form a homogeneous mixture. This has particular consequences in almond orchards, where any foreign material left on the orchard floor is collected with the nuts during the mechanical harvest of the crop. At the hulling facility, the woody chips and shreds are difficult to separate from the almond hulls. Since almond hulls are sold to dairies as a feed supplement, excessive amounts of fiber, such as that provided by the woody material, reduce the food and economic value of the supplement. Moreover, to the extent that the chips or shreds can be separated from the hulls at the hulling facility, they pose an expensive storage and disposal problem.
While some chipping and shredding machines are designed to be operated in remote field locations, they cannot pick up branches from the ground and feed them into the chipper. Nor are such devices designed to process material while passing through a field. Conventional mobile chippers and shredders are simply parked for on-site operation, and then after finishing, moved on to a new location. No continuous field processing of material spread over a large area is possible.
Consequently, the need exists for a mobile device, adapted to pass through an orchard or field, and while in motion, continuously shred pruned material arranged in rows or piles.
The need also exists for a mobile field shredder which can shred branches into particles having a size and consistency whereby they can be deposited directly onto the ground, for rapid decomposition and soil enrichment.
The need further exists for a mobile field shredder which can produce shredded particles of a selected size and consistency.
The need also exists for a field shredder which can pick up variably-sized cuttings from the ground, and process them continuously without need for adjustment or interruption.
Lastly, the need exists for a detachable field shredder which can be front mounted on and coupled to a transport vehicle, providing both mobility and operational power for the shredder.
The field shredder of the present invention is properly characterized as a shredder, yet has some of the characteristics of a chipper.
The shredder of the present invention is constructed on a mobile shredder frame. The shredder frame is preferably detachably coupled to the front end of a tractor, or other transport vehicle. In that manner, the tractor may be used for other purposes throughout the growing year and the shredder may be stored until needed, or transported to another location for use with a different tractor.
Rotary feeder means is mounted on the front end of the shredder frame for picking up the pruned branches from the ground. The feeder means includes an upper feeder roller and a counter-rotating lower feeder roller. The feeder rollers are elongated, have parallel axes of rotation, and are mounted transversely with respect to the direction of travel of the shredder frame. In this manner, the central portions of the rollers are adapted to engage a row of stacked, pruned branches as the mobile frame is moved through an orchard, a vineyard, or other agricultural setting where cuttings are so row-arranged.
The upper feeder roller has plurality of circumferentially-spaced gripping plates. The plates extend longitudinally along the full length of the roller, and project in perpendicular fashion from its outer periphery. The plates are provided with an outer edge, having teeth or serrations for engaging the branches. The upper feeder roller is mounted on a pair of hydraulically damped sub-frames, pivotally mounted to the shredder frame. In response to variably-sized incoming branches, the upper feeder roller and the sub-frames rotate upwardly or downwardly to accommodate larger or smaller branches.
The lower feeder roller includes a plurality of radially extending tines for mechanically engaging and lifting the branches from the ground. A guide plate, including plural slots to accommodate rotational passage of the tines therethrough, is located above and slightly rearwardly from the lower feed roller. Branches lifted by the tines are engaged by the gripping plates of the upper roller, and are fed rearwardly, between the gripping plates of the upper roller and the guide plate.
A shredding chamber, mounted in the central and rear portions of the shredder frame, has a front inlet adjacent the output of the feeder means. The shredding chamber is defined by lateral end plates spanned by upper and lower shrouds. The chamber also includes an acuate, rear-positioned chamber screen, which provides an outlet for the shredded branch particles.
Housed within the shredding chamber are a first shredder roller and a second shredder roller. The shredder rollers have longitudinal axes of rotation parallel to the upper and lower feeder rollers. The first and second rollers are mounted for rotation on roller drive shafts, passing through both end s of the shredding chamber. Shredder roller pulleys are provided on the end extremities of these drive shafts.
A gear box is mounted in the central region of the shredder frame, above the shredding chamber. The gear box has an input drive shaft, and a pair of output drive shafts. Rotational power may be provided to the input drive shaft by an engine. This engine may be mounted either on the shredder, or on an auxiliary vehicle which transports the shredder. The output drive shafts extend laterally from either side of the gear box, past both end plates of the shredding chamber. A drive pulley is located on the outer end extremity of each drive shafts. A drive belt interconnects the drive pulley with the roller pulleys for the shredder rollers. The shredder rollers are thereby driven in tandem, in such a manner that their upper portions rotate rearwardly, and their lower portions rotate forwardly.
The first roller is provided with a plurality of knife blocks, strategically located in semi-helical rows on the outer periphery of the roller. The second roller is similarly equipped with knife blocks, but the height of these blocks is somewhat greater than the height of the knife blocks on the first roller. Each of the knife blocks has a sharp leading edge, which is arranged in spaced relation from the upper and lower shrouds and the arcuate chamber screen. These knife blocks both cut and shred the incoming branches, as they pass through the shredding chamber, first rearwardly from the first roller to the second roller, and then forwardly from the second roller to the first roller.
The residence time of material within the shredding chamber determines the size and consistency of the discharged particles. If the perforations within the chamber screen are enlarged in size, the residence time will be reduced and the particle size increased. If the perforations within the chamber screen are reduced in size, the residence time will be increased and the particle size decreased.